1. Field of the Invention
The present invention relates to a color liquid crystal display panel and, particularly, to a color filter substrate of a color liquid crystal display panel of an In-Plane-Switching type.
2. Description of the Prior Art
A color filter (CF) substrate of a color liquid crystal display (LCD) cell includes a red (R) color layer, a green (G) color layer and a blue (B) color layer. In order to obtain desired chromaticity of these color layers, each color layer has been formed of transparent resin such as acrylic resin containing a pigment and an additive such as a dispersing agent. Since it is required, in order to realize a uniform cell gap of the LCD cell, to make a surface of the CF substrate on which the color layers are formed as flat as possible, the respective color layers are formed such that they have the same thickness.
When the requirements of chromaticity and thickness of the respective color layers are to be satisfied predominantly, specific resistance, that is, resistivity, of each of the color layers may substantially vary in a range of 107xcx9c1014 (xcexa9.cm). Particularly, it is known that the resistivity of the red color layer is very large compared with those of the green color layer and the blue color layer. It is further known that such large difference in resistivity between the color layers leads to a difference in amount of electric charge between the color layers and, therefore, there is a problem that a distribution of spacer particles in a cell gap becomes varied in dispersing spacer particles by the dry dispersing method, causing a display performance of the color LCD panel to be degraded.
In order to solve the above problem, Japanese Unexamined Patent Publication No. H11-38420 discloses a technique in which a light shield such as a black matrix is charged in one polarity and spacer particles are charged in the opposite polarity such that the spacer particles are selectively dispersed on only the light shield.
On the other hand, Japanese Patent No. 3044788 discloses a technique in which an influence of voltage drop in color layers of a color filter used in a LCD panel is reduced by reducing resistivity of the respective color layers although a drive mode thereof is not limited to the In-Plane-Switching (IPS) type. In this Japanese patent, the resistivity of each of R, G and B color layers is restricted to 108 (xcexa9.cm) or less by dispersing particles of indium-tin-oxide (ITO) in the respective color layers.
When the resistivity of the respective color layers are substantially reduced as in this patent, the IPS mode drive cannot be established. Therefore, the technique disclosed in Japanese Patent No. 3044788 cannot be applied to the IPS type color LCD cell.
Under the circumstances, an object of the present invention is to provide a color filter having color layers, which can satisfy desired chromaticity thereof without reducing resistivity of the respective color layers too much and which have uniform spacer distribution even when spacer particles are dispersed by using the dry dispersing method.
The present invention is based on the fact, which has been confirmed by experiments conducted by the present inventors, that, by combining color layers in such a way that the resistivity of each color layer is 1010 (xcexa9.cm) or less and a ratio of the resistivity between the respective color layers becomes 600 or less, the chromaticity of the respective color layers can be satisfied and the influence of the spacer distribution on the display characteristics of the color LCD panel is negligible.
An IPS type color LCD panel according to a first aspect of the present invention includes color layers provided on a substrate to provide three primary colors (red, green and blue), a black matrix provided on the substrate and burying at least gaps between the color layers and an insulating film covering a surface of the substrate including the color layers and the black matrix, wherein maximum value of the resistivity of each of the color layers is set to 6xc3x97102 or less times minimum value of the resistivity thereof. With this setting of the maximum value of the resistivity of each color layer with respect to the minimum value thereof, there is substantially no variation of display, which is caused by variation of distribution of dispersed spacer particles.
According to a second aspect of the present invention, the IPS type color LCD panel is featured by comprising a color filter substrate having a red color layer, a green color layer and a blue color layer arranged thereon such that the color layers are separated from each other by a black matrix layer, an electrode substrate arranged in an opposing relation to the color filter substrate through spacer particles and having pixel electrodes and a liquid crystal layer pinched between the color filter substrate and the electrode substrate, wherein a maximum resistivity of each color layer is set to 6xc3x97102 or less times a minimum resistivity thereof.
The IPS type color LCD panel according to the second aspect of the present invention is further featured by that spacer particles are dispersed by dry-dispersing method. The present invention is further featured by that the respective color layers and the black matrix layer on the color filter substrate are commonly covered by an overcoat layer. The present invention is further featured by that an alignment layer is formed on the overcoat layer. Furthermore, the present invention is featured by that the color layers are formed of transparent resin containing pigments and dispersing agent, respectively.
According to a third aspect of the present invention, the IPS type color LCD panel is featured by comprising a color filter substrate having a red color layer, a green color layer and a blue color layer arranged thereon such that the color layers are separated from each other by a black matrix layer, an active matrix substrate arranged in an opposing relation to the color filter substrate through spacer particles and having a plurality of pixel electrodes connected to a plurality of switching elements and a common electrode and a liquid crystal layer pinched between the color filter substrate and the active matrix substrate, wherein a maximum resistivity of each color layer is set to 6xc3x97102 or less times a minimum resistivity thereof.
In this IPS type color LCD panel, the resistivity of each color layer is 1010 (xcexa9.cm) or more and, preferably, in a range from 1xc3x971011 (xcexa9.cm) to 1xc3x971016 (xcexa9.cm). More preferably, the resistivity of the red color layer is in a range from 1xc3x971013 (xcexa9.cm) to 1xc3x971014 (xcexa9.cm) and the resistivity of the green color layer as well as the blue color layer is in a range from 1xc3x971012 (xcexa9.cm) to 1xc3x971013 (xcexa9.cm).